1. Field of the Invention
This invention relates to a collapsible structure, including but not limited to a pushchair for children, wherein it comprises:                an upright;        a sliding block sliding on the upright along an axis, the sliding block being blocked in rotation around this axis;        at least one collapsible leg, unfolding from a collapsed position near the upright, to an unfolded position distanced from the upright;        a jointed structure for the unfolding of the leg comprising, seen according to a direction different from said axis, a jointed deployment triangle;        
this deployment triangle comprising:                a first side attached to the upright between a first joint located on the upright and a second joint located on a point of the sliding block;        a second side jointed on the sliding block by the second joint;        a third side jointed on the upright by the first joint and on the second side by a third joint.        
2. Field of the Invention
Such a structure is known from FR 2.259.001. A structure of this type allows a relatively simple unfolding of a collapsible structure, such as a pushchair for children. As a matter of fact, the unfolding of the legs of the pushchair is ensured by a straightforward linear movement of the sliding block along the upright. This type of folding, similar to an umbrella, makes it possible to avoid the inconveniences known to current so-called “umbrella-fold” buggies, in which a plurality of unfolding operations must be performed in order to reach the unfolded position of the structure.
However, the seats of the above-mentioned type are not entirely satisfactory. Indeed, the second and third jointed sides of the deployment triangle of such seats are constituted of simple connecting bars. These connecting bars are respectively linked to the sliding block and to the upright via simple hinges. The rigidity of the structure in the unfolded position is therefore ensured by this set of connecting bars and hinges. Thus, if these hinges are not stiffened, the deployment triangle, and consequently the related leg, would lack circumferential rigidity with respect to the upright. It is then necessary to use complex rigidifying means for the hinges, as for example a mono-block structure equipped with channel shaped supports, integral with the sliding block.
The prior art also includes patent FR 2.167.594, which discloses a collapsible structure that does not have a rigid guiding triangle. The only supposed guiding triangle extends from three points respectively linking (i) a point located at the lowest end of the L-shaped backbone (defining the linear unfolding axis of the pushchair), (ii) a point on the horizontal portion of the L-shaped backbone, and finally (iii) a point on the support for one of the rear wheels. In this structure, there is an obligation that one of the segments constituting the said triangle is non-rigid, or flexible, as one of the points constituting the vertices of the triangle is not on the rotation axis of the triangle segment opposite to such point. As appears in FIG. 3, such flexibility could be provided by an additional line hinge close to the ball hinge in the corner. Thus, this guiding triangle does in no way constitute a rigid structure.
The main purpose of the invention is to resolve this inconvenience, by providing an easily collapsible structure, which is rigidified in the unfolded position via simple, inexpensive and light means.